Sustainable phosphorus management of horse paddocks at Julmyra

Abstract: Horse keeping is gaining an increasing interest in Sweden. During 2004 to 2010 the number of horses increased with 10 - 20 %, and was estimated to be 362 700 in 2010. Julmyra Horse Center (JHC), situated in Heby municipality, is a gated community for people sharing a large interest for horses and a vision of a sustainable horse management has been formulated. This study evaluates how the horse keeping of today at JHC, and how an expansion of the horse keeping may affect the risk of enhanced phosphorus load to the nearby lake system Vansjön – Nordsjön. The risks associated with outdoor horse keeping are an accumulation of phosphorus in the soil profile caused by dung deposition and roughage residues, and treading damages, that might contribute to eutrophication. The soils in the area are mainly lowland soils with high humus content. The mineral fractions are dominated by sand, sandy loam and moraine. There are no regulations regarding livestock densities for outdoor horse keeping in Sweden, but maximum 2-10 horses/hectare is recommended in order to retain a vegetation cover in paddocks. The livestock density at JHC today is 17.5 horses per hectare, causing treading damages in most paddocks. The paddocks receive approximately a yearly input of 38 – 53 kg P/hectare with the current horse density. The soil phosphorus status in most of the paddocks (P-AL) was low to moderate, 4.2 – 7.9 mg/100 g soil. However, in areas where an accumulation of phosphorus by dung deposition had occurred over a long period of time, and for a loose housing system the P-AL values were higher (17.7 and 16.3 mg/100 g soil). In these areas, the values of phosphorus sorption capacity in the soil were low or moderate (1.1 and 4.5) and the degree of soil phosphorus saturation quite high (up to 22.0 %). It was concluded that there is a continuous accumulation of phosphorus in the horse paddocks which is not sustainable in the long-term. In order to make the paddock management at JHC sustainable suggested countermeasures are increased paddock areas, cleaning of dung and roughage residues and establishment of grass vegetated buffer strips between paddocks and the watercourse.